Shared folders not visible in mobile devices

Hello
Zimbra + Zextras are in a dual cpu (4+4 cores) HP DL 180 with 12 Gb Ram and there's not issues in hard (disks works fine) 1+0 w/spare raid for data and 1 w/spare for SO (centos last version updated) backed in a NAS with about 400 user.
Customer say us that cannot view shared folders synced in mobile devices. Its the same in all devices (IOS/Android/BBerry) while tey appear without any problem in client and web interface. Is there an issue or is not posssible to do it?
Best regards.